The present invention relates generally to computed tomography imaging and, more particularly, to a detector cell for sensing thermal changes in response to the absorption of HF electromagnetic energy for use with computed tomography systems.
Typically, in computed tomography (CT) imaging systems, an x-ray source emits a fan-shaped beam towards a subject or object, such as a patient or a piece of luggage. Hereinafter the terms xe2x80x9csubjectxe2x80x9d and xe2x80x9cobjectxe2x80x9d shall include anything capable of being imaged. The beam, after being attenuated by the subject, impinges upon an array of radiation detectors. The intensity of the attenuated beam radiation received at the detector array is typically dependent upon the attenuation of the x-ray beam by the subject. Each detector element of the detector array produces a separate electrical signal indicative of the attenuated beam received by each detector element. The electrical signals are transmitted to a data processing system for analysis which ultimately results in the formation of an image.
Generally, the x-ray source and the detector array are rotated about the gantry within an imaging plane and around the subject. X-ray sources typically include x-ray tubes, which emit the x-ray beam at a focal point. X-ray detectors typically include a collimator for collimating x-ray beams received at the detector, a scintillator for converting x-rays to light energy adjacent the collimator, and photodiodes for receiving the light energy from the adjacent scintillator. Each scintillator of a scintillator array converts x-rays to light energy. Each scintillator discharges light energy to a photodiode adjacent thereto. Each photodiode detects the light energy and generates a corresponding electrical signal. The outputs of the photodiodes are then transmitted to a data processing system.
With these known scintillators, the scintillating component must be of sufficient thickness to generate the requisite efficient x-ray detection. As a result, a minimum scintillating material thickness is necessary for proper signal to noise generation by the photodiode. The minimum requirements yield higher costs as well as limit the ability to reduce the overall detector cell size and spatial resolution of the detector. Furthermore, detection inefficiencies in this two step detection process, x-rays to light and light to electrical signals, has efficiency losses resulting in a diagnostic image of poorer quality or lower sensitivity.
High density materials may be advantageously used in a detection cell as these materials may absorb HF electromagnetic energy in relatively thin cross-sections. As a result, smaller detector cells can be fabricated increasing system resolution. Moreover, use of materials that change in temperature upon the absorption of HF electromagnetic energy allows for use of thermal sensing components rather than photodiodes thereby producing output signals more indicative of the HF electromagnetic energy detected resulting in a more sensitive and a diagnostic image of greater sensitivity.
It would therefore be desirable to design a detector cell for sensing thermal differentials in the detector cell resulting from the absorption of HF electromagnetic energy thereby providing improved, higher resolution, and more sensitive detector signal output to a data processing system of a CT system.
The present invention is directed to a detector cell overcoming the aforementioned drawbacks that generates electrical signals indicative of HF electromagnetic energy absorbed by the detector as defined by thermal differentials within the detector.
In accordance with one aspect of the present invention a CT detector cell is provided and includes an HF electromagnetic energy absorption component comprised of a material configured to change in temperature in response to absorption of HF electromagnetic energy. The CT detector cell further includes a thermal sensing component configured to detect a change in the temperature of the absorption component and output a signal indicative of the HF electromagnetic energy absorbed by the HF electromagnetic energy absorption component.
In accordance with yet another aspect of the present invention, a CT system includes a rotatable gantry having an opening therein and configured to receive a subject to be scanned. The system also includes a subject positioner configured to place the subject to be scanned within the opening and an HF electromagnetic energy projection source configured to project HF electromagnetic energy toward the subject to be scanned. The system also includes an HF electromagnetic energy detector array having a plurality of detector cells which is configured to absorb HF electromagnetic energy passing through the subject to be scanned. Each detector cell includes a HF electromagnetic energy absorption component and a thermal sensing component. The CT system further includes a data acquisition system (DAS) connected to the detector array and configured to receive electrical signals from each thermal sensing component indicative of a change in temperature of a corresponding HF electromagnetic energy absorption component. An image reconstructor is also provided and connected to the DAS and configured to reconstruct an image of the subject from the electrical signals received by the DAS.
In accordance with a further aspect of the present invention, a method of manufacturing a radiation detector sensor array for use with CT systems includes the step of determining a high density material capable of changing in temperature upon absorption of radiation. The method further includes forming an absorption array having a plurality of absorption cells from the high density material. The method also includes coupling a thermal sensing array having a plurality of thermal sensing cells to the absorption array such that each thermal sensing cell corresponds to an absorption cell.
In accordance with yet another aspect of the present invention, a detector array for a CT system includes means for absorbing HF electromagnetic energy and means for experiencing thermal differentials in response to absorbed HF electromagnetic energy. The detector array also includes means for detecting the thermal differentials as well as means for outputting a signal indicative of the HF electromagnetic energy absorbed as defined by detected thermal differentials.